A Cochlear implant (CI) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. The cochlear implant is often referred to as a bionic ear. Unlike hearing aids, the cochlear implant does not amplify sound, but works by directly stimulating any functioning auditory nerves inside the cochlea with electrical impulses.
External components of the cochlear implant include a microphone, speech processor and transmitter which also allows an individual to adjust the sound for quality and amplification.
According to researchers at the University of Michigan, approximately 100,000 people worldwide have received cochlear implants, with recipients split almost evenly between children and adults. The vast majority are in developed countries due to the high cost of the device, surgery and post-implantation therapy — Mexico had performed only 55 cochlear implant operations by the year 2000 (Berruecos 2000). China will be having 15,000 cochlear implant surgeries on children, which are being paid for by a Taiwanese philanthropist. There is concern that the follow-up services in China are not adequate to meet the needs of cochlear implanted children. A small percentage of those now have bilateral implants, or one on each cochlea. Bilateral cochlear implants are a growing trend globally, Cochlear Americas reported that 15% of their 2006 sales in the United States were for bilateral implants.
Individuals who have acquired deaf blindness (loss of hearing and vision combined) may find cochlear implants a radical improvement in their daily life. It may provide them with more information for safety, communication, balance, orientation and mobility and promote interaction within their environment and with other people, reducing isolation. Having more auditory information that they may be familiar with may provide them independent gathering of information to become more independent.
The implant often gives recipients additional auditory information, which may include sound discrimination fine enough to understand speech in quiet environments. Though sufficient, and quality, post-implantation rehabilitative therapy is a critical factor affecting the success rate.
The introduction of cochlear implants has seen the renewal of a century-old debate about models of deafness that often pits hearing parents of deaf children against the Deaf community. There is debate whether Cochlear implants are ethically sound; see Ethics below.
Parts of the Cochlear Implant
The implant is surgically placed under the skin behind the ear. The basic parts of the device include:
- a microphone which picks up sound from the environment
- a speech processor which selectively filters sound to prioritize audible speech and sends the electrical sound signals through a thin cable to the transmitter,
- a transmitter, which is a coil held in position by a magnet placed behind the external ear, and transmits the processed sound signals to the internal device by electromagnetic induction,
- a receiver and stimulator secured in bone beneath the skin, which converts the signals into electric impulses and sends them through an internal cable to electrodes,
- an array of up to 22 electrodes wound through the cochlea, which send the impulses to the nerves in the scala tympani and then directly to the brain through the auditory nerve system.
Candidates for Cochlear Implants
There are a number of factors that determine the degree of success to expect from the operation and the device itself. Cochlear implant centers determine implant candidacy on an individual basis and take into account a person’s hearing history, cause of hearing loss, amount of residual hearing, speech recognition ability, health status, and family commitment to aural habilitation/rehabilitation.
A prime candidate for a cochlear implant is described as:
- Having severe to profound sensorineural hearing impairment in both ears
- having a functioning auditory nerve
- having lived a short amount of time without hearing (approximately 70+ decibel loss, on average)
- having good speech, language, and communication skills, or in the case of infants and young children, having a family willing to work toward speech and language skills with therapy
- not benefiting enough from other kinds of hearing aids
- having no medical reason to avoid surgery
- living in or desiring to live in the “hearing world”
- having realistic expectations about results
- having the support of family and friends
- having appropriate services set up for post-cochlear implant aural rehabilitation (through a speech language pathologist, deaf educator, or auditory verbal therapist).
Type of hearing impairment
People with mild or moderate sensorineural hearing loss are generally not candidates for cochlear implantation. After the implant is put into place, sound no longer travels via the ear canal and middle ear but will be picked up by a microphone and sent through the device’s speech processor to the implant’s electrodes inside the cochlea. Thus, most candidates have been diagnosed with profound sensorineural hearing loss.
The presence of auditory nerve fibers is essential to the functioning of the device: if these are damaged to such an extent that they cannot receive electrical stimuli, the implant will not work. A small number of individuals with severe auditory neuropathy may also benefit from cochlear implants.
Age of Cochlear Implant Recipient
Cost of Cochlear Implants
With careful selection of candidates, the risks of implantation are minimized.
Cochlear Implant Manufacturers